org.apache.hadoop.hbase.PerformanceEvaluationDoubleTable.java Source code

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/**
 * Copyright 2007 The Apache Software Foundation
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.hbase;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.io.PrintStream;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Date;
import java.util.List;
import java.util.Map;
import java.util.Random;
import java.util.TreeMap;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hbase.client.Get;
import org.apache.hadoop.hbase.client.HBaseAdmin;
import org.apache.hadoop.hbase.client.HTable;
import org.apache.hadoop.hbase.client.Put;
import org.apache.hadoop.hbase.client.Result;
import org.apache.hadoop.hbase.client.ResultScanner;
import org.apache.hadoop.hbase.client.Scan;
import org.apache.hadoop.hbase.filter.PageFilter;
import org.apache.hadoop.hbase.filter.WhileMatchFilter;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.hbase.util.FSUtils;
import org.apache.hadoop.hbase.util.Hash;
import org.apache.hadoop.hbase.util.MurmurHash;

import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.JobContext;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
import org.apache.hadoop.mapreduce.lib.reduce.LongSumReducer;
import org.apache.hadoop.util.LineReader;

/**
 * Script used evaluating HBase performance and scalability.  Runs a HBase
 * client that steps through one of a set of hardcoded tests or 'experiments'
 * (e.g. a random reads test, a random writes test, etc.). Pass on the
 * command-line which test to run and how many clients are participating in
 * this experiment. Run <code>java PerformanceEvaluation --help</code> to
 * obtain usage.
 * 
 * <p>This class sets up and runs the evaluation programs described in
 * Section 7, <i>Performance Evaluation</i>, of the <a
 * href="http://labs.google.com/papers/bigtable.html">Bigtable</a>
 * paper, pages 8-10.
 * 
 * <p>If number of clients > 1, we start up a MapReduce job. Each map task
 * runs an individual client. Each client does about 1GB of data.
 */
public class PerformanceEvaluationDoubleTable implements HConstants {
    protected static final Log LOG = LogFactory.getLog(PerformanceEvaluationDoubleTable.class.getName());

    private static final int ROW_LENGTH = 1000;
    private static final int ONE_GB = 1024 * 1024 * 1000;
    private static final int ROWS_PER_GB = ONE_GB / ROW_LENGTH;

    public static final byte[] FAMILY_NAME = Bytes.toBytes("info");

    public static final byte[] QUALIFIER_NAME = Bytes.toBytes("index");
    public static final byte[] QUALIFIER_NAME_DATA = Bytes.toBytes("data");
    public static final byte[] FAMILY_NAME_AND_QUALIFIER_NAME_DATA = Bytes.toBytes("info:data");
    public static final byte[] FAMILY_NAME_AND_QUALIFIER_NAME = Bytes.toBytes("info:index");

    protected static final HTableDescriptor TABLE_DESCRIPTOR;
    static {
        TABLE_DESCRIPTOR = new HTableDescriptor("TestTable");
        TABLE_DESCRIPTOR.addFamily(new HColumnDescriptor(FAMILY_NAME));
    }

    private static final String RANDOM_READ = "randomRead";
    private static final String RANDOM_SEEK_SCAN = "randomSeekScan";
    private static final String RANDOM_READ_MEM = "randomReadMem";
    private static final String RANDOM_WRITE = "randomWrite";
    private static final String SEQUENTIAL_READ = "sequentialRead";
    private static final String SEQUENTIAL_WRITE = "sequentialWrite";
    private static final String SCAN = "scan";

    private static final List<String> COMMANDS = Arrays.asList(new String[] { RANDOM_READ, RANDOM_SEEK_SCAN,
            RANDOM_READ_MEM, RANDOM_WRITE, SEQUENTIAL_READ, SEQUENTIAL_WRITE, SCAN });

    volatile HBaseConfiguration conf;
    private boolean miniCluster = false;
    private boolean nomapred = false;
    private int N = 1;
    private int R = ROWS_PER_GB;
    private static final Path PERF_EVAL_DIR = new Path("performance_evaluation");

    /**
     * Regex to parse lines in input file passed to mapreduce task.
     */
    public static final Pattern LINE_PATTERN = Pattern
            .compile("startRow=(\\d+),\\s+" + "perClientRunRows=(\\d+),\\s+totalRows=(\\d+),\\s+clients=(\\d+)");

    /**
     * Enum for map metrics.  Keep it out here rather than inside in the Map
     * inner-class so we can find associated properties.
     */
    protected static enum Counter {
        /** elapsed time */
        ELAPSED_TIME,
        /** number of rows */
        ROWS
    }

    /**
     * Constructor
     * @param c Configuration object
     */
    public PerformanceEvaluationDoubleTable(final HBaseConfiguration c) {
        this.conf = c;
    }

    /**
     * Implementations can have their status set.
     */
    static interface Status {
        /**
         * Sets status
         * @param msg status message
         * @throws IOException
         */
        void setStatus(final String msg) throws IOException;
    }

    /**
     *  This class works as the InputSplit of Performance Evaluation
     *  MapReduce InputFormat, and the Record Value of RecordReader. 
     *  Each map task will only read one record from a PeInputSplit, 
     *  the record value is the PeInputSplit itself.
     */
    public static class PeInputSplit extends InputSplit implements Writable {
        private int startRow = 0;
        private int rows = 0;
        private int totalRows = 0;
        private int clients = 0;

        public PeInputSplit() {
            this.startRow = 0;
            this.rows = 0;
            this.totalRows = 0;
            this.clients = 0;
        }

        public PeInputSplit(int startRow, int rows, int totalRows, int clients) {
            this.startRow = startRow;
            this.rows = rows;
            this.totalRows = totalRows;
            this.clients = clients;
        }

        public void readFields(DataInput in) throws IOException {
            this.startRow = in.readInt();
            this.rows = in.readInt();
            this.totalRows = in.readInt();
            this.clients = in.readInt();
        }

        public void write(DataOutput out) throws IOException {
            out.writeInt(startRow);
            out.writeInt(rows);
            out.writeInt(totalRows);
            out.writeInt(clients);
        }

        public long getLength() throws IOException, InterruptedException {
            return 0;
        }

        public String[] getLocations() throws IOException, InterruptedException {
            return new String[0];
        }

        public int getStartRow() {
            return startRow;
        }

        public int getRows() {
            return rows;
        }

        public int getTotalRows() {
            return totalRows;
        }

        public int getClients() {
            return clients;
        }
    }

    /**
     *  InputFormat of Performance Evaluation MapReduce job.
     *  It extends from FileInputFormat, want to use it's methods such as setInputPaths(). 
     */
    public static class PeInputFormat extends FileInputFormat<NullWritable, PeInputSplit> {

        public List<InputSplit> getSplits(JobContext job) throws IOException {
            // generate splits
            List<InputSplit> splitList = new ArrayList<InputSplit>();

            for (FileStatus file : listStatus(job)) {
                Path path = file.getPath();
                FileSystem fs = path.getFileSystem(job.getConfiguration());
                FSDataInputStream fileIn = fs.open(path);
                LineReader in = new LineReader(fileIn, job.getConfiguration());
                int lineLen = 0;
                while (true) {
                    Text lineText = new Text();
                    lineLen = in.readLine(lineText);
                    if (lineLen <= 0) {
                        break;
                    }
                    Matcher m = LINE_PATTERN.matcher(lineText.toString());
                    if ((m != null) && m.matches()) {
                        int startRow = Integer.parseInt(m.group(1));
                        int rows = Integer.parseInt(m.group(2));
                        int totalRows = Integer.parseInt(m.group(3));
                        int clients = Integer.parseInt(m.group(4));

                        LOG.debug("split[" + splitList.size() + "] " + " startRow=" + startRow + " rows=" + rows
                                + " totalRows=" + totalRows + " clients=" + clients);

                        PeInputSplit newSplit = new PeInputSplit(startRow, rows, totalRows, clients);
                        splitList.add(newSplit);
                    }
                }
                in.close();
            }

            LOG.info("Total # of splits: " + splitList.size());
            return splitList;
        }

        public RecordReader<NullWritable, PeInputSplit> createRecordReader(InputSplit split,
                TaskAttemptContext context) {
            return new PeRecordReader();
        }

        public static class PeRecordReader extends RecordReader<NullWritable, PeInputSplit> {
            private boolean readOver = false;
            private PeInputSplit split = null;
            private NullWritable key = null;
            private PeInputSplit value = null;

            public void initialize(InputSplit split, TaskAttemptContext context)
                    throws IOException, InterruptedException {
                this.readOver = false;
                this.split = (PeInputSplit) split;
            }

            public boolean nextKeyValue() throws IOException, InterruptedException {
                if (readOver) {
                    return false;
                }

                key = NullWritable.get();
                value = (PeInputSplit) split;

                readOver = true;
                return true;
            }

            public NullWritable getCurrentKey() throws IOException, InterruptedException {
                return key;
            }

            public PeInputSplit getCurrentValue() throws IOException, InterruptedException {
                return value;
            }

            public float getProgress() throws IOException, InterruptedException {
                if (readOver) {
                    return 1.0f;
                } else {
                    return 0.0f;
                }
            }

            public void close() throws IOException {
                // do nothing
            }
        }
    }

    /**
     * MapReduce job that runs a performance evaluation client in each map task.
     */
    public static class EvaluationMapTask extends Mapper<NullWritable, PeInputSplit, LongWritable, LongWritable> {

        /** configuration parameter name that contains the command */
        public final static String CMD_KEY = "EvaluationMapTask.command";
        private String cmd;
        private PerformanceEvaluationDoubleTable pe;

        protected void setup(Context context) throws IOException, InterruptedException {
            this.cmd = context.getConfiguration().get(CMD_KEY);
            this.pe = new PerformanceEvaluationDoubleTable(new HBaseConfiguration(context.getConfiguration()));
        }

        protected void map(NullWritable key, PeInputSplit value, final Context context)
                throws IOException, InterruptedException {

            Status status = new Status() {
                public void setStatus(String msg) {
                    context.setStatus(msg);
                }
            };

            // Evaluation task
            long elapsedTime = this.pe.runOneClient(this.cmd, value.getStartRow(), value.getRows(),
                    value.getTotalRows(), status);
            // Collect how much time the thing took. Report as map output and
            // to the ELAPSED_TIME counter.
            context.getCounter(Counter.ELAPSED_TIME).increment(elapsedTime);
            context.getCounter(Counter.ROWS).increment(value.rows);
            context.write(new LongWritable(value.startRow), new LongWritable(elapsedTime));
            context.progress();
        }
    }

    /*
     * If table does not already exist, create.
     * @param c Client to use checking.
     * @return True if we created the table.
     * @throws IOException
     */
    private boolean checkTable(HBaseAdmin admin) throws IOException {
        boolean tableExists = admin.tableExists(TABLE_DESCRIPTOR.getName());
        if (!tableExists) {
            admin.createTable(TABLE_DESCRIPTOR);
            LOG.info("Table " + TABLE_DESCRIPTOR + " created");
        }
        return !tableExists;
    }

    /*
     * We're to run multiple clients concurrently.  Setup a mapreduce job.  Run
     * one map per client.  Then run a single reduce to sum the elapsed times.
     * @param cmd Command to run.
     * @throws IOException
     */
    private void runNIsMoreThanOne(final String cmd)
            throws IOException, InterruptedException, ClassNotFoundException {
        checkTable(new HBaseAdmin(conf));
        if (this.nomapred) {
            doMultipleClients(cmd);
        } else {
            doMapReduce(cmd);
        }
    }

    /*
     * Run all clients in this vm each to its own thread.
     * @param cmd Command to run.
     * @throws IOException
     */
    @SuppressWarnings("unused")
    private void doMultipleClients(final String cmd) throws IOException {
        final List<Thread> threads = new ArrayList<Thread>(this.N);
        final int perClientRows = R / N;
        for (int i = 0; i < this.N; i++) {
            Thread t = new Thread(Integer.toString(i)) {

                public void run() {
                    super.run();
                    PerformanceEvaluationDoubleTable pe = new PerformanceEvaluationDoubleTable(conf);
                    int index = Integer.parseInt(getName());
                    try {
                        long elapsedTime = pe.runOneClient(cmd, index * perClientRows, perClientRows, perClientRows,
                                new Status() {
                                    public void setStatus(final String msg) throws IOException {
                                        LOG.info("client-" + getName() + " " + msg);
                                    }
                                });
                        LOG.info("Finished " + getName() + " in " + elapsedTime + "ms writing " + perClientRows
                                + " rows");
                    } catch (IOException e) {
                        throw new RuntimeException(e);
                    }
                }
            };
            threads.add(t);
        }
        for (Thread t : threads) {
            t.start();
        }
        for (Thread t : threads) {
            while (t.isAlive()) {
                try {
                    t.join();
                } catch (InterruptedException e) {
                    LOG.debug("Interrupted, continuing" + e.toString());
                }
            }
        }
    }

    /*
     * Run a mapreduce job.  Run as many maps as asked-for clients.
     * Before we start up the job, write out an input file with instruction
     * per client regards which row they are to start on.
     * @param cmd Command to run.
     * @throws IOException
     */
    private void doMapReduce(final String cmd) throws IOException, InterruptedException, ClassNotFoundException {
        Path inputDir = writeInputFile(this.conf);
        this.conf.set(EvaluationMapTask.CMD_KEY, cmd);
        Job job = new Job(this.conf);
        job.setJarByClass(PerformanceEvaluationDoubleTable.class);
        job.setJobName("HBase Performance Evaluation");

        job.setInputFormatClass(PeInputFormat.class);
        PeInputFormat.setInputPaths(job, inputDir);

        job.setOutputKeyClass(LongWritable.class);
        job.setOutputValueClass(LongWritable.class);

        job.setMapperClass(EvaluationMapTask.class);
        job.setReducerClass(LongSumReducer.class);

        job.setNumReduceTasks(1);

        job.setOutputFormatClass(TextOutputFormat.class);
        TextOutputFormat.setOutputPath(job, new Path(inputDir, "outputs"));

        job.waitForCompletion(true);
    }

    /*
     * Write input file of offsets-per-client for the mapreduce job.
     * @param c Configuration
     * @return Directory that contains file written.
     * @throws IOException
     */
    private Path writeInputFile(final Configuration c) throws IOException {
        FileSystem fs = FileSystem.get(c);
        if (!fs.exists(PERF_EVAL_DIR)) {
            fs.mkdirs(PERF_EVAL_DIR);
        }
        SimpleDateFormat formatter = new SimpleDateFormat("yyyyMMddHHmmss");
        Path subdir = new Path(PERF_EVAL_DIR, formatter.format(new Date()));
        fs.mkdirs(subdir);
        Path inputFile = new Path(subdir, "input.txt");
        PrintStream out = new PrintStream(fs.create(inputFile));
        // Make input random.
        Map<Integer, String> m = new TreeMap<Integer, String>();
        Hash h = MurmurHash.getInstance();
        int perClientRows = (this.R / this.N);
        try {
            for (int i = 0; i < 10; i++) {
                for (int j = 0; j < N; j++) {
                    String s = "startRow=" + ((j * perClientRows) + (i * (perClientRows / 10)))
                            + ", perClientRunRows=" + (perClientRows / 10) + ", totalRows=" + this.R + ", clients="
                            + this.N;
                    int hash = h.hash(Bytes.toBytes(s));
                    m.put(hash, s);
                }
            }
            for (Map.Entry<Integer, String> e : m.entrySet()) {
                out.println(e.getValue());
            }
        } finally {
            out.close();
        }
        return subdir;
    }

    /*
     * A test.
     * Subclass to particularize what happens per row.
     */
    static abstract class Test {
        protected final Random rand = new Random(System.currentTimeMillis());
        protected final int startRow;
        protected final int perClientRunRows;
        protected final int totalRows;
        private final Status status;
        protected HBaseAdmin admin;
        protected HTable table;
        protected volatile HBaseConfiguration conf;

        Test(final HBaseConfiguration conf, final int startRow, final int perClientRunRows, final int totalRows,
                final Status status) {
            super();
            this.startRow = startRow;
            this.perClientRunRows = perClientRunRows;
            this.totalRows = totalRows;
            this.status = status;
            this.table = null;
            this.conf = conf;
        }

        private String generateStatus(final int sr, final int i, final int lr) {
            return sr + "/" + i + "/" + lr;
        }

        protected int getReportingPeriod() {
            return this.perClientRunRows / 10;
        }

        void testSetup() throws IOException {
            this.admin = new HBaseAdmin(conf);
            this.table = new HTable(conf, TABLE_DESCRIPTOR.getName());
            this.table.setAutoFlush(false);
            this.table.setWriteBufferSize(1024 * 1024 * 12);
            this.table.setScannerCaching(30);
        }

        void testTakedown() throws IOException {
            this.table.flushCommits();
        }

        /*
         * Run test
         * @return Elapsed time.
         * @throws IOException
         */
        long test() throws IOException {
            long elapsedTime;
            testSetup();
            long startTime = System.currentTimeMillis();
            try {
                int lastRow = this.startRow + this.perClientRunRows;
                // Report on completion of 1/10th of total.
                for (int i = this.startRow; i < lastRow; i++) {
                    testRow(i);
                    if (status != null && i > 0 && (i % getReportingPeriod()) == 0) {
                        status.setStatus(generateStatus(this.startRow, i, lastRow));
                    }
                }
                elapsedTime = System.currentTimeMillis() - startTime;
            } finally {
                testTakedown();
            }
            return elapsedTime;
        }

        /*
         * Test for individual row.
         * @param i Row index.
         */
        abstract void testRow(final int i) throws IOException;

        /*
         * @return Test name.
         */
        abstract String getTestName();
    }

    class RandomSeekScanTest extends Test {
        RandomSeekScanTest(final HBaseConfiguration conf, final int startRow, final int perClientRunRows,
                final int totalRows, final Status status) {
            super(conf, startRow, perClientRunRows, totalRows, status);
        }

        void testRow(final int i) throws IOException {
            Scan scan = new Scan(getRandomRow(this.rand, this.totalRows));
            scan.addColumn(FAMILY_NAME, QUALIFIER_NAME);
            scan.setFilter(new WhileMatchFilter(new PageFilter(120)));
            ResultScanner s = this.table.getScanner(scan);
            //int count = 0;
            for (Result rr = null; (rr = s.next()) != null;) {
                // LOG.info("" + count++ + " " + rr.toString());
            }
            s.close();
        }

        protected int getReportingPeriod() {
            // 
            return this.perClientRunRows / 100;
        }

        String getTestName() {
            return "randomSeekScanTest";
        }
    }

    class RandomReadTest extends Test {
        RandomReadTest(final HBaseConfiguration conf, final int startRow, final int perClientRunRows,
                final int totalRows, final Status status) {
            super(conf, startRow, perClientRunRows, totalRows, status);
        }

        void testRow(final int i) throws IOException {
            Get get = new Get(getRandomRow(this.rand, this.totalRows));
            get.addColumn(FAMILY_NAME, QUALIFIER_NAME);
            this.table.get(get);
        }

        protected int getReportingPeriod() {
            // 
            return this.perClientRunRows / 100;
        }

        String getTestName() {
            return "randomRead";
        }
    }

    public static byte[] format(final long number) {
        byte[] b = new byte[10];
        long d = Math.abs(number);
        for (int i = b.length - 1; i >= 0; i--) {
            b[i] = (byte) ((d % 10) + '0');
            d /= 10;
        }
        return b;
    }

    class RandomWriteTest extends Test {
        RandomWriteTest(final HBaseConfiguration conf, final int startRow, final int perClientRunRows,
                final int totalRows, final Status status) {
            super(conf, startRow, perClientRunRows, totalRows, status);
        }

        void testRow(final int i) throws IOException {
            byte[] row = getRandomRow(this.rand, this.totalRows);
            Put put = new Put(row);
            put.add(FAMILY_NAME, QUALIFIER_NAME, format(this.rand.nextLong()));
            put.add(FAMILY_NAME, QUALIFIER_NAME_DATA, generateValue(this.rand));
            table.put(put);
        }

        String getTestName() {
            return "randomWrite";
        }
    }

    class ScanTest extends Test {
        private ResultScanner testScanner;

        void fillValue() {
            long startTime = System.currentTimeMillis();

            int lastRow = this.startRow + this.perClientRunRows;
            // Report on completion of 1/10th of total.
            for (int i = this.startRow; i < lastRow; i++) {
                byte[] row = getRandomRow(this.rand, this.totalRows);
                Put put = new Put(row);
                put.add(FAMILY_NAME, QUALIFIER_NAME, format(this.rand.nextLong()));
                put.add(FAMILY_NAME, QUALIFIER_NAME_DATA, generateValue(this.rand));

                try {
                    table.put(put);
                    if (i % 1000 == 0)
                        LOG.debug("#############################put :" + i);
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }

        }

        ScanTest(final HBaseConfiguration conf, final int startRow, final int perClientRunRows, final int totalRows,
                final Status status) {
            super(conf, startRow, perClientRunRows, totalRows, status);

        }

        void testSetup() throws IOException {
            super.testSetup();
            this.fillValue();
            Scan scan = new Scan(format(this.startRow));
            scan.addColumn(FAMILY_NAME, QUALIFIER_NAME);
            this.testScanner = table.getScanner(scan);
        }

        void testTakedown() throws IOException {
            if (this.testScanner != null) {
                this.testScanner.close();
            }
            super.testTakedown();
        }

        void testRow(final int i) throws IOException {
            testScanner.next();
        }

        String getTestName() {
            return "scan";
        }
    }

    class SequentialReadTest extends Test {
        SequentialReadTest(final HBaseConfiguration conf, final int startRow, final int perClientRunRows,
                final int totalRows, final Status status) {
            super(conf, startRow, perClientRunRows, totalRows, status);
        }

        void testRow(final int i) throws IOException {
            Get get = new Get(format(i));
            get.addColumn(FAMILY_NAME, QUALIFIER_NAME);
            table.get(get);
        }

        String getTestName() {
            return "sequentialRead";
        }
    }

    class SequentialWriteTest extends Test {
        SequentialWriteTest(final HBaseConfiguration conf, final int startRow, final int perClientRunRows,
                final int totalRows, final Status status) {
            super(conf, startRow, perClientRunRows, totalRows, status);
        }

        void testRow(final int i) throws IOException {
            Put put = new Put(format(i));
            put.add(FAMILY_NAME, QUALIFIER_NAME, format(this.rand.nextLong()));
            put.add(FAMILY_NAME, QUALIFIER_NAME_DATA, generateValue(this.rand));

            table.put(put);
        }

        String getTestName() {
            return "sequentialWrite";
        }
    }

    /*
     * Format passed integer.
     * @param number
     * @return Returns zero-prefixed 10-byte wide decimal version of passed
     * number (Does absolute in case number is negative).
     */
    public static byte[] format(final int number) {
        byte[] b = new byte[10];
        int d = Math.abs(number);
        for (int i = b.length - 1; i >= 0; i--) {
            b[i] = (byte) ((d % 10) + '0');
            d /= 10;
        }
        return b;
    }

    /*
     * This method takes some time and is done inline uploading data.  For
     * example, doing the mapfile test, generation of the key and value
     * consumes about 30% of CPU time.
     * @return Generated random value to insert into a table cell.
     */
    public static byte[] generateValue(final Random r) {
        byte[] b = new byte[ROW_LENGTH];
        r.nextBytes(b);
        return b;
    }

    static byte[] getRandomRow(final Random random, final int totalRows) {
        return format(random.nextInt(Integer.MAX_VALUE) % totalRows);
    }

    long runOneClient(final String cmd, final int startRow, final int perClientRunRows, final int totalRows,
            final Status status) throws IOException {
        status.setStatus("Start " + cmd + " at offset " + startRow + " for " + perClientRunRows + " rows");
        long totalElapsedTime = 0;
        if (cmd.equals(RANDOM_READ)) {
            Test t = new RandomReadTest(this.conf, startRow, perClientRunRows, totalRows, status);
            totalElapsedTime = t.test();
        } else if (cmd.equals(RANDOM_READ_MEM)) {
            throw new UnsupportedOperationException("Not yet implemented");
        } else if (cmd.equals(RANDOM_WRITE)) {
            Test t = new RandomWriteTest(this.conf, startRow, perClientRunRows, totalRows, status);
            totalElapsedTime = t.test();
        } else if (cmd.equals(SCAN)) {
            Test t = new ScanTest(this.conf, startRow, perClientRunRows, totalRows, status);
            totalElapsedTime = t.test();
        } else if (cmd.equals(SEQUENTIAL_READ)) {
            Test t = new SequentialReadTest(this.conf, startRow, perClientRunRows, totalRows, status);
            totalElapsedTime = t.test();
        } else if (cmd.equals(SEQUENTIAL_WRITE)) {
            Test t = new SequentialWriteTest(this.conf, startRow, perClientRunRows, totalRows, status);
            totalElapsedTime = t.test();
        } else if (cmd.equals(RANDOM_SEEK_SCAN)) {
            Test t = new RandomSeekScanTest(this.conf, startRow, perClientRunRows, totalRows, status);
            totalElapsedTime = t.test();
        } else {
            throw new IllegalArgumentException("Invalid command value: " + cmd);
        }
        status.setStatus("Finished " + cmd + " in " + totalElapsedTime + "ms at offset " + startRow + " for "
                + perClientRunRows + " rows");
        return totalElapsedTime;
    }

    private void runNIsOne(final String cmd) {
        Status status = new Status() {
            public void setStatus(String msg) throws IOException {
                LOG.info(msg);
            }
        };

        HBaseAdmin admin = null;
        try {
            admin = new HBaseAdmin(this.conf);
            checkTable(admin);
            runOneClient(cmd, 0, this.R, this.R, status);
        } catch (Exception e) {
            LOG.error("Failed", e);
        }
    }

    private void runTest(final String cmd) throws IOException, InterruptedException, ClassNotFoundException {
        if (cmd.equals(RANDOM_READ_MEM)) {
            // For this one test, so all fits in memory, make R smaller (See
            // pg. 9 of BigTable paper).
            R = (this.R / 10) * N;
        }

        try {
            if (N == 1) {
                // If there is only one client and one HRegionServer, we assume nothing
                // has been set up at all.
                runNIsOne(cmd);
            } else {
                // Else, run 
                runNIsMoreThanOne(cmd);
            }
        } finally {

        }
    }

    private void printUsage() {
        printUsage(null);
    }

    private void printUsage(final String message) {
        if (message != null && message.length() > 0) {
            System.err.println(message);
        }
        System.err.println("Usage: java " + this.getClass().getName() + " [--master=HOST:PORT] \\");
        System.err.println("  [--miniCluster] [--nomapred] [--rows=ROWS] <command> <nclients>");
        System.err.println();
        System.err.println("Options:");
        System.err.println(" master          Specify host and port of HBase " + "cluster master. If not present,");
        System.err.println("                 address is read from configuration");
        System.err.println(" miniCluster     Run the test on an HBaseMiniCluster");
        System.err.println(" nomapred        Run multiple clients using threads " + "(rather than use mapreduce)");
        System.err.println(" rows            Rows each client runs. Default: One million");
        System.err.println();
        System.err.println("Command:");
        System.err.println(" randomRead      Run random read test");
        System.err.println(" randomReadMem   Run random read test where table " + "is in memory");
        System.err.println(" randomSeekScan  Run random seek and scan 100 test");
        System.err.println(" randomWrite     Run random write test");
        System.err.println(" sequentialRead  Run sequential read test");
        System.err.println(" sequentialWrite Run sequential write test");
        System.err.println(" scan            Run scan test");
        System.err.println();
        System.err.println("Args:");
        System.err.println(" nclients        Integer. Required. Total number of " + "clients (and HRegionServers)");
        System.err.println("                 running: 1 <= value <= 500");
        System.err.println("Examples:");
        System.err.println(" To run a single evaluation client:");
        System.err.println(" $ bin/hbase " + "org.apache.hadoop.hbase.PerformanceEvaluation sequentialWrite 1");
    }

    private void getArgs(final int start, final String[] args) {
        if (start + 1 > args.length) {
            throw new IllegalArgumentException("must supply the number of clients");
        }

        N = Integer.parseInt(args[start]);
        if (N < 1) {
            throw new IllegalArgumentException("Number of clients must be > 1");
        }

        // Set total number of rows to write.
        this.R = this.R * N;
    }

    private int doCommandLine(final String[] args) {
        // Process command-line args. TODO: Better cmd-line processing
        // (but hopefully something not as painful as cli options).    
        int errCode = -1;
        if (args.length < 1) {
            printUsage();
            return errCode;
        }

        try {
            for (int i = 0; i < args.length; i++) {
                String cmd = args[i];
                if (cmd.equals("-h") || cmd.startsWith("--h")) {
                    printUsage();
                    errCode = 0;
                    break;
                }

                final String miniClusterArgKey = "--miniCluster";
                if (cmd.startsWith(miniClusterArgKey)) {
                    this.miniCluster = true;
                    continue;
                }

                final String nmr = "--nomapred";
                if (cmd.startsWith(nmr)) {
                    this.nomapred = true;
                    continue;
                }

                final String rows = "--rows=";
                if (cmd.startsWith(rows)) {
                    this.R = Integer.parseInt(cmd.substring(rows.length()));
                    continue;
                }

                if (COMMANDS.contains(cmd)) {
                    getArgs(i + 1, args);
                    runTest(cmd);
                    errCode = 0;
                    break;
                }

                printUsage();
                break;
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

        return errCode;
    }

    /**
     * @param args
     */
    public static void main(final String[] args) {
        HBaseConfiguration c = new HBaseConfiguration();
        System.exit(new PerformanceEvaluationDoubleTable(c).doCommandLine(args));
    }
}